1. Field of the Invention
This invention relates to a tool holder for tapping and boring using a swinging cutting method, which can be used for a tapping machine, a reaming machine, a machining center, etc.
2. Description of the Prior Art
Heretofore, known tapping operations have not been sufficiently smooth to discharge cutting dust. In addition, the cutting tool is liable to be broken by excessive resistance offered against cutting. Therefore, the tapping operation has been regarded as troublesome, and particular attention has been required when tapping to form a small diameter thread.
Various research and investigations have been conducted to facilitate the tapping operation, and a swinging cutting method has been developed, which is thought to be the most effective method. The swinging cutting method is one in which a tapping operation is performed by causing forced swinging of the cutting blade (or tap) or workpiece. It is well known in the art that when this method is employed, the theoretical resistance offered against cutting is reduced, the discharge of the cutting dust is improved, satisfactory tapping free from formation of burrs can be obtained, and even small diameter threads can be readily formed. A great variety of tapping machines, reaming machines, tool holders, etc. which adopt the swinging cutting method have been developed.
In the prior art apparatus, however, the cutter blade is rotated while the workpiece is swung by the provision of separate drive sources for rotating the cutter blade and swinging the workpiece. Therefore, the apparatus is inevitably complicated in construction and increased in size. An apparatus also has been developed which uses a single drive source for both rotating and swinging the cutter blade. In this case, however, the rotation and the swinging of the cutter blade are not smooth. In addition, the speed of swinging is close to that of rotation. Therefore, it is impossible to obtain theoretical effects of the swinging. The apparatus, therefore, lacks practicality, and its practical use is substantially infeasible.